YOU SAID:

you know it's cold outside when you go out and it's cold

INTO JAPANESE

外出して寒いとき、外は寒いのを知っている

BACK INTO ENGLISH

When you go out and it's cold, you know it's cold outside.

INTO JAPANESE

外出して寒いとき、外が寒いのが分かります。

BACK INTO ENGLISH

When you go out and it's cold, you can see that it's cold outside.

INTO JAPANESE

外出して寒いとき、外が寒いことがわかります。

BACK INTO ENGLISH

When you go out and it's cold, you can see that it's cold outside.